Storage virtualization is known as a technique to transfer data from a source storage apparatus to a destination storage apparatus without interruption of accesses from a host computer to data in the storage apparatuses and for the host computer to use the data successively after the migration.
In the meanwhile, for the storage system to provide the host with volumes, there is a known practice of forming a hierarchically tiered pool from multiple drives different in performance capability in the storage system to provision the host with virtual volumes configured from the pool.
The storage system analyzes input/output (I/O) loads from the host to the virtual volumes and automatically relocates pages with higher I/O load to higher-class tiers composed of resources of expensive disks having higher performance capability and pages with lower I/O load to lower-class tiers composed of resources of inexpensive disks having lower performance capability (data relocation among tiers). This technique effectively satisfies performance requirements at a lower total cost of ownership (TCO).
US 2011/0320754 A (PTL1) discloses an exemplary method of migration of volume data in a tier-managed storage apparatus. This literature discloses comparing the tier configuration of the source storage apparatus prior to the start of the migration with the tier configuration of the destination storage apparatus to transfer data from the source storage apparatus to the destination storage apparatus based on the result of the comparison.